EXAFS and XANES spectroscopy will be used to characterize the structure of the complexes formed when vanadium(IV) and vanadium(V) bind to small peptides that are derived from the protein tyrosine phosphatase consensus sequence. These measurements, when coupled with EPR, spin-echo, and 51V NMR measurements, will serve to define the nature of the vanadium-peptide interactions. This structural information is needed to characterize the nature of vanadium mediated insulin mimesis.